Take the mantis to your LFS. Many people want them and you should get some credit.
The brown algae is most likely diatoms (not an algae). The brown you see are the frustules of the diatom. Your will likely see these die off and may see them reoccur a couple time in the first 6 months or so. Higher flow helps keep them suspended. There food source is silica which will eventually be depleted (assuming you are not adding it) to the point they can't sustain their numbers.
Okay im a retard lol. They are just big copepods... Sigh, what a noon awell.
Got the fuge setup with LR and macro algea. Looks good actually. I'm also running a carbon pad and phosphate pad cut to size
Also bought 1.5kg more rock with favia coral on it. It has this cool creature on it. It looks like eyelids and closes really quick if I go anywhere near it. Pics to come!!!